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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

High-latitude ion convection in the nighttime F region

A large data base of Atmosphere Explorer C measurements of the bulk ion velocity vector in the high-latitude F region has been examined. The concept of shear and rotational flow reversals is expanded upon to determine the extent to which the boundary between antisunward and sunward convection (i.e., a polar cap boundary) is an electrostatic equipotential. A most important factor in characterizing the nature of the large-scale geometrical configuration of the nighttime F region convection is the location and extent of quasi-equipotential regions of the convection reversal boundary.

Heelis, R. A.↗
NASA NTRS1980

F region airglow - Are ground-based observations consistent with recent satellite results

The Atmosphere Explorer photochemistry is used to interpret simultaneous observations made at the Arecibo Observatory of the OI (6300 A) and NI (5200 A) airglow surface brightness and electron density and temperature profiles measured by incoherent scatter radar. It was found that the theory and the experiment agree for the 5200-A emission; however, it was not possible to obtain to a complete agreement for the 6300-A nightglow. It is suggested that the source of the discrepancy results from one of the parameters used to calculate the production rate of O(lD); the data show evidence of an asymmetrical behavior of the ionosphere between times when the F layer is descending and when it is ascending, with asymmetry probably reflecting the effects of transport on molecular ion densities in the bottom side of the F region.

Cogger, L. L.↗
NASA NTRS1981

UV chromospheric and circumstellar diagnostic features among F supergiant stars

A survey of F supergiant stars to evaluate the extension of chromospheric and circumstellar characteristics commonly observed in the slightly cooler G, K, and M supergiant is discussed. An ultraviolet survey was elected since UV features of Mg II and Fe II might persist in revealing outer atmosphere phenomena even among F supergiants. The encompassed spectral types F0 to G0, and luminosity classes Ib, Ia, and Ia-0. In addition, the usefulness of the emission line width-to-luminosity correlation for the G-M stars in both the Ca II and Mg II lines is examined.

Stencel, R. E.↗
NASA NTRS1981

A theoretical study of the high-latitude winter F region at solar minimum for low magnetic activity

A simple plasma convection model is combined with an ionospheric-atmospheric composition model in order to study the high-latitude winter F region at the solar minimum for low magnetic activity. The high latitude ionospheric features, such as the main trough, the ionization hole, the tongue of ionization, the aurorally produced ionization peaks, and the universal time effects are a natural consequence of the competition between the various chemical and transport processes known to be operating in the high-latitude ionosphere. In the polar hole, the F region peak electron density is below 300 km, and the dominant process at 300 km for NO(+) ions is diffusion.

Sojka, J. J.↗
NASA NTRS1981

The F-ring of Saturn

The existence of a split and twisted F-ring, located outside of Saturn's A-ring, as observed during the Voyager Saturn fly-by, is reported. The peculiarities in the appearance of the F-ring are described, and include: (1) the presence of one or more loose strands of matter reaching up to 100 km away from it; (2) a fairly sharp kink or step in the main ring; and (3) the presence of local bright clumps and streaks in the otherwise rather dark ring. It is proposed that, the loose strands are probably the result of the action of the local magnetic field on sufficiently small charged particles of the ring; and that the sharp kinks and steps are a result of sudden changes in the solar magnetic field, carried by the solar wind, which compress temporarily the planetary magnetosphere.

Smoluchowski, R.↗
NASA NTRS1981

Limited evaluation of an F-14A airplane utilizing an aileron-rudder interconnect control system in the landing configuration

A flight test was conducted for preliminary evaluation of an aileron-rudder interconnect (ARI) control system for the F-14A airplane in the landing configuration. Two ARI configurations were tested in addition to the standard F-14 flight control system. Results of the flight test showed marked improvement in handling qualities when the ARI systems were used. Sideslip due to adverse yaw was considerably reduced, and airplane turn rate was more responsive to pilot lateral control inputs. Pilot comments substantiated the flight data and indicated that the ARI systems were superior to the standard control system in terms of pilot capability to make lateral offset corrections and heading changes on final approach.

Kelley, W. W.↗
NASA NTRS1981

A presently available energy supply for high temperature environment (550-1000 deg F)

Sodium-sulfur cells attractive electric energy storage device for long service, are discussed. The state of art is given. More than 200 Wh/kg cells were tested. The known range of working temperature is 550 to 750 F. Self-discharge is quite nonexistent for months in operation. The technical basis for expecting an operating range up to 1,000 F under a high pressure atmosphere is given. Possibilities to adapt size and characteristics to particular interplanetary missions are discussed.

Jacquelin, J.↗
NASA NTRS1982

Preliminary design notes on a low F-number EMR

Conceptual design studies were completed on a new Electrostatic Membrane Reflector, EMR. This new model incorporates both a preformed, curved membrane reflector and membrane control surface. This improved model is the second step toward a high precision large space antenna that could eventually exhibit a performance in terms of aperture diameter to surface quality exceeding 1,000,000. Design trades indicate that the goal of a low ratio of focal length to aperture diameter (f sub n) can be achieved while operating in a humid sea-level environment. A nominal surface quality of 1.0 mm (RMS) is possible using available off-the-shelf commercial membranes. Both the membrane reflector and control electrode surface are fabricated from 12 gore segments and attached to the available 12 sided, 4.88 m diameter rim. The preferred conceptual design has a f sub n = 1.0. The 4.88 m aperture is performed with a centerline displacement of 0.306 m. The nominal spacing between the membrane reflector and the electrode control surface is 50.8 mm. The centerline membrane displacement from its performed to its tensioned, smooth shape is about 3 mm. The membrane tensioning is achieved by application of an electrostatic pressure of 2.6 N/sq cm and a voltage of about 38 kV.

Mihora, D. J.↗
NASA NTRS1982

Effective temperatures of A and F stars

Effective temperatures of late A and early F stars are determined from the observed fluxes in the visual at 1900 A and 1420 A. The observed ratios are compared with those calculated by Kurucz (1979). A correction of the theoretical fluxes at 1900 A brings the effective temperatures obtained from different ratios into reasonable agreement. The effective temperatures determined in this way for late A stars agree well with those obtained from the optical region. For F stars, however, the effective temperatures obtained from the UV are found to be higher than those obtained from the optical region if radiative equilibrium models are used for the comparison. It is thought that this discrepancy may derive from the effects of temperature, pressure, and absorption coefficient inhomogeneities caused by convection.

Boehm-Vitense, E.↗
NASA NTRS1982

Selected results of the F-15 propulsion interactions program

A better understanding of propulsion system/airframe flow interactions could aid in the reduction of aircraft drag. For this purpose, NASA and the United States Air Force have conducted a series of wind-tunnel and flight tests on the F-15 airplane. This paper presents a correlation of flight test data from tests conducted at the NASA Dryden Flight Research Facility of the Ames Research Center, with data obtained from wind-tunnel tests. Flights were made at stabilized Mach numbers around 0.6, 0.9, 1.2, and 1.5 with accelerations up to near Mach number 2. Wind-tunnel tests used a 7.5 percent-scale F-15 inlet/airframe model. Flight and wind-tunnel pressure coefficients showed good agreement in most cases. Correlation of interaction effects caused by changes in cowl angle, angle-of-attack, and Mach number are presented. For the afterbody region, the pressure coefficients on the nozzle surfaces were influenced by boattail angles and Mach number. Boundary-layer thickness decreased as angle of attack increased above 4 deg.

Webb, L. D.↗
NASA NTRS1982

Seasonal dependence of the distribution of large-scale plasma depletions in the low-latitude F region

From several years of Atmosphere Explorer data, it is shown that large-scale plasma density depletions (horizontal scale greater than 1000km) in the nocturnal F region occur mainly during the first half of the night. The geomagnetic latitude of these depletions depends on season: at solstice periods the occurrence is mainly in the summer hemisphere and at equinoxes mainly on the geomagnetic equator. Large-scale depletions occur most often at longitudes characterized by a large magnetic declination. The large-scale plasma depletions are interpreted to be a consequence of imposed upward drift which raises the F region above the satellite trajectory. This interpretation is tested by calculating the vertical ion drift velocity imposed by zonal and meridional winds and electrostatic fields, with allowance for the effects of diffusion. The calculations reveal a correspondence between the locations of maxima in the calculated vertical ion drift velocity and the large-scale plasma depletions.

Dachev, T. P.↗
NASA NTRS1982

Dynamics Explorer observations of equatorial spread F - Evidence for drift waves

Recent DE-2 data from the Langmuir probe, vector electric field, and ion drift meter instruments are employed to study equatorial spread F in the frequency regime of the low frequency drift and the lower hybrid drift instabilities. Strong electron density gradients topside equatorial F region correspond to regions of high electric field waves and large ion drift velocities. The electric field waves are seen in two distinct wavelength ranges which correspond to the parameter regimes of the low frequency drift and the lower hybrid drift instabilities. In the smaller of the two wavelength ranges the lower hybrid drift instability is found to be unstable, based on the ion drift velocity and the other plasma parameters measured on DE-2, and using published theory. Thus there is experimental evidence that the lower hybrid drift instability may produce the observed short wavelength waves without invoking a cascading mechanism.

Hoegy, W. R.↗
NASA NTRS1983

NASA F-106B lightning tests

Lightning simulation ground tests conducted on the NASA F-106B research aircraft to elicit natural strikes are summarized. The purpose of the test program was to measure the response of the aircraft's electromagnetic sensors and interior wire circuits to a controlled ground test environment that simulates the electromagnetic effects of a lightning strike. Both direct attachment and radiated field tests were conducted. In most cases, the aircraft's engine was running and test data were gathered simultaneously from NASA and MCAIR sensors on both the aircraft's own instrumentation system and the remote MCAIR computer-controlled data acquisition system. During the direct attachment tests, the input inductance, output condition (hard-wired or spark gap), and the output location were varied to provide a wide variety of test conditons. The radiated tests to the isolated aircraft were conducted to excite and measure the natural resonances of the F-106B aircraft.

Heady, B. D.↗
NASA NTRS1982

A numerical study of Saturn's F-ring

The short term effects of 'shepherding' satellites is examined in the general case where all bodies move along eccentric orbits by analyzing the motion of a ring of particles as their orbits evolve under the gravitational perturbations of the shepherds. This computational approach makes ring evolution calculations extremely efficient numerically, and provides added insight into the nature of this two-body interaction. The procedure is analyzed and applied to several possible configurations of ring and shepherd orbits, emphasizing the F ring. If the F ring-to-satellite distance changes significantly due to eccentricities, the ring can break up into periodic clumps in an azimuthal domain which trails the satellite. This region may lag somewhat in longitude. The perturbations may cause the ring to vary significantly in a width, and can impart a significant, but probably time-variable, eccentricity to the ring.

Showalter, M. R.↗
NASA NTRS1983

Saturn's E, G, and F rings - Modulated by the plasma sheet?

Saturn's broad E ring, the narrow G ring, and the structured and apparently time-variable F ring(s) contain many micron and submicron-sized particles, which make up the 'visible' component. These rings (or ring systems) are in direct contact with magnetospheric plasma. Fluctuations in the plasma density and/or mean energy, due to magnetospheric and solar wind processes, may induce stochastic charge variations on the dust particles, which in turn lead to an orbit perturbation and spatial diffusion. In addition, Coulomb drag forces may be important, in particular for the E ring. The possibility that electromagnetic effects may play a role in determining the F ring structure and its possible time variations is critically examined. Sputtering of micron-sized dust particles in the E ring by magnetospheric ions yields lifetimes of 100 to 10,000 years. This effect as well as the plasma induced transport processes require an active source for the E ring, probably Enceladus.

Morfill, G. E.↗
NASA NTRS1983

Photochemistry of N2(+) in the daytime F region

The photochemistry of N2(+) in the daytime F region continues to be a source of concern due primarily to the uncertain roles of the metastable O+(2D) ion and possible vibrational excitation. This investigation adopts a unique subset of data from the Atmospheric Explorer C satellite that spans distinct regions near the low-latitude F peak wherein either chemical reactions or electron processes alternatively control the N2(+) abundances. Concentrations of N2(+) calculated according to current theory and including recent laboratory data for O+(2D) losses via N2 are found to exceed ionospheric observations between 220 and 400 km by a factor near 2. Relevant characteristics of the basic molecular ion concentration measurements are described, along with an analysis for select orbits conducted according to current photochemical equilibrium theory. Possible simple modifications of this theory are discussed in terms of the constraints suggested by the nature of the observations.

Breig, E. L.↗
NASA NTRS1983

Bottomside sinusoidal irregularities in the equatorial F region

By using the Ogo 6 satellite, McClure and Hanson (1973) have discovered sinusoidal irregularities in the equatorial F region ion number density. In the present investigation, a description is provided of the properties of a distinct category of sinusoidal irregularities found in equatorial data from the AE-C and AE-E satellites. The observed scale sizes vary from about 300 m to 3 km in the direction perpendicular to B, overlapping with and extending the range observed by using Ogo 6. Attention is given to low and high resolution data, a comparison with Huancayo ionograms, the confinement of 'bottomside sinusoidal' (BSS) irregularities essentially to the bottomside of the F layer, spectral characteristics, and BSS, scintillation, and ionosonde observations.

Valladares, C. E.↗
NASA NTRS1984

Light variations of the population II F-type supergiant HD 46703

Photometric monitoring has revealed brightness variations of 0.1 m on a time scale of weeks for HD 46703, a metal-deficient F-type field analog of the stars lying above the horizontal branch in globular clusters. It is suggested that HD 46703 belongs to the '89 Her' class of luminous F-type variables. Since HD 46703 is unquestionably a halo object, it is almost certainly a low-mass star. It is suggested that it, and probably the other 89 Her variables, are masquerading as supergiants during their final evolution off the asymptotic giant branch.

Bond, H. E.↗